Role of PIP2 and Bin1 in T-tubule Remodeling During Heart Failure Development

The goal of the project is to investigate the proteins involved in T-tubule formation and maintenance as well as the specific molecular signaling that induces T-tubule disruption in heart failure (HF) in response to hypertension (HTN). T-tubule formation and maintenance is critical to effective and efficient heart function as T-tubules are essential players in excitation-contraction coupling (ECC) and normal Ca2+ cycling in cardiac myocytes. It is thought that the cardiac isoform of the structural protein Bin1 binds to PIP2 (phosphatidylinositol 4,5-bisphosphate) as critical components of T-tubule formation. Studies will use protein samples from cardiac, skeletal muscle, and whole brain tissues of rats to investigate the interaction between the cardiac isoform of Bin1 and PIP2. PIP2 is confirmed to bind to Exon 10 in Isoform 8 of Bin1 in skeletal muscle, serving as a positive control. No whole brain isoforms contain Exon 10 and there is no evidence of PIP2 binding; thus, brain protein samples will be used as a negative control. While cardiac Bin1 does not contain exon 10 (isoform has not yet been identified or sequenced in its entirety), preliminary evidence suggests cardiac Bin1 binds to PIP2. PIP strips, a type of phospholipid array, will test for 18 different phosphoinositols (PIs), and will be used to investigate the ways in which Bin1 binds to PIP2. The project will also investigate the expression of the enzyme PI4K (phosphoinositol-4-kinase), which is a precursor to PIP2, in rat hearts during early and late stages of HF development. Preliminary studies suggest that PI4K is downregulated in both animal models and in humans in HF. Results from measurement of PI4K in rat and human models of normal and diseased states may demonstrate that downregulation of PI4K in the disease mechanism may result in T-tubule remodeling and disruption. Therapeutic intervention to stabilize or even reverse the disruption of the T-tubule network in HF patients is of particular importance due to the lack of new potential targets for drug therapy over the last twenty years.